The art of formulating lubricating oil compositions for industrial equipment has become more complex as a result of increased government and user environmental standards and increased user performance requirements. For example, many end users seek lubricants that do not employ metallic detergents and dispersants that are typically used to keep deposit-forming precursors in an oil away from working surfaces. Ashless or non-metal containing dispersants and detergents, however, tend to be effective in emulsifying water in the oil. Industrial oils such as gear, hydraulic, and circulating oils typically are required to be capable of separating from water in order that any water contamination arising during use does not adversely impact equipment operation and durability. Thus, additives that may enhance one property of a lubricating composition may adversely effect another property.
Another required property for industrial oils is rust inhibition. Again, some end users desire lubricant compositions that employ ashless rust inhibitors. Unfortunately, experience has shown that lubricants with ashless rust inhibitors are not as effective in inhibiting rust as lubricants using metallic sulfonate or metallic carbonate rust inhibitors. Thus use of an additive that may be environmentally desirable may result in a lubricating composition that does not meet certain specific performance requirements.
One object of the present invention is to provide an ashless industrial oil lubricating composition that has good water separability characteristics.
Another object is to provide an ashless lubricating composition that has good rust inhibition.
Yet another object is to provide an industrial oil composition that has good thermal and oxidative stability.